diff options
Diffstat (limited to 'drivers/md/dm-cache-target.c')
| -rw-r--r-- | drivers/md/dm-cache-target.c | 3480 |
1 files changed, 3480 insertions, 0 deletions
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c new file mode 100644 index 000000000..911f73f7e --- /dev/null +++ b/drivers/md/dm-cache-target.c @@ -0,0 +1,3480 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2012 Red Hat. All rights reserved. + * + * This file is released under the GPL. + */ + +#include "dm.h" +#include "dm-bio-prison-v2.h" +#include "dm-bio-record.h" +#include "dm-cache-metadata.h" +#include "dm-io-tracker.h" + +#include <linux/dm-io.h> +#include <linux/dm-kcopyd.h> +#include <linux/jiffies.h> +#include <linux/init.h> +#include <linux/mempool.h> +#include <linux/module.h> +#include <linux/rwsem.h> +#include <linux/slab.h> +#include <linux/vmalloc.h> + +#define DM_MSG_PREFIX "cache" + +DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle, + "A percentage of time allocated for copying to and/or from cache"); + +/*----------------------------------------------------------------*/ + +/* + * Glossary: + * + * oblock: index of an origin block + * cblock: index of a cache block + * promotion: movement of a block from origin to cache + * demotion: movement of a block from cache to origin + * migration: movement of a block between the origin and cache device, + * either direction + */ + +/*----------------------------------------------------------------*/ + +/* + * Represents a chunk of future work. 'input' allows continuations to pass + * values between themselves, typically error values. + */ +struct continuation { + struct work_struct ws; + blk_status_t input; +}; + +static inline void init_continuation(struct continuation *k, + void (*fn)(struct work_struct *)) +{ + INIT_WORK(&k->ws, fn); + k->input = 0; +} + +static inline void queue_continuation(struct workqueue_struct *wq, + struct continuation *k) +{ + queue_work(wq, &k->ws); +} + +/*----------------------------------------------------------------*/ + +/* + * The batcher collects together pieces of work that need a particular + * operation to occur before they can proceed (typically a commit). + */ +struct batcher { + /* + * The operation that everyone is waiting for. + */ + blk_status_t (*commit_op)(void *context); + void *commit_context; + + /* + * This is how bios should be issued once the commit op is complete + * (accounted_request). + */ + void (*issue_op)(struct bio *bio, void *context); + void *issue_context; + + /* + * Queued work gets put on here after commit. + */ + struct workqueue_struct *wq; + + spinlock_t lock; + struct list_head work_items; + struct bio_list bios; + struct work_struct commit_work; + + bool commit_scheduled; +}; + +static void __commit(struct work_struct *_ws) +{ + struct batcher *b = container_of(_ws, struct batcher, commit_work); + blk_status_t r; + struct list_head work_items; + struct work_struct *ws, *tmp; + struct continuation *k; + struct bio *bio; + struct bio_list bios; + + INIT_LIST_HEAD(&work_items); + bio_list_init(&bios); + + /* + * We have to grab these before the commit_op to avoid a race + * condition. + */ + spin_lock_irq(&b->lock); + list_splice_init(&b->work_items, &work_items); + bio_list_merge(&bios, &b->bios); + bio_list_init(&b->bios); + b->commit_scheduled = false; + spin_unlock_irq(&b->lock); + + r = b->commit_op(b->commit_context); + + list_for_each_entry_safe(ws, tmp, &work_items, entry) { + k = container_of(ws, struct continuation, ws); + k->input = r; + INIT_LIST_HEAD(&ws->entry); /* to avoid a WARN_ON */ + queue_work(b->wq, ws); + } + + while ((bio = bio_list_pop(&bios))) { + if (r) { + bio->bi_status = r; + bio_endio(bio); + } else + b->issue_op(bio, b->issue_context); + } +} + +static void batcher_init(struct batcher *b, + blk_status_t (*commit_op)(void *), + void *commit_context, + void (*issue_op)(struct bio *bio, void *), + void *issue_context, + struct workqueue_struct *wq) +{ + b->commit_op = commit_op; + b->commit_context = commit_context; + b->issue_op = issue_op; + b->issue_context = issue_context; + b->wq = wq; + + spin_lock_init(&b->lock); + INIT_LIST_HEAD(&b->work_items); + bio_list_init(&b->bios); + INIT_WORK(&b->commit_work, __commit); + b->commit_scheduled = false; +} + +static void async_commit(struct batcher *b) +{ + queue_work(b->wq, &b->commit_work); +} + +static void continue_after_commit(struct batcher *b, struct continuation *k) +{ + bool commit_scheduled; + + spin_lock_irq(&b->lock); + commit_scheduled = b->commit_scheduled; + list_add_tail(&k->ws.entry, &b->work_items); + spin_unlock_irq(&b->lock); + + if (commit_scheduled) + async_commit(b); +} + +/* + * Bios are errored if commit failed. + */ +static void issue_after_commit(struct batcher *b, struct bio *bio) +{ + bool commit_scheduled; + + spin_lock_irq(&b->lock); + commit_scheduled = b->commit_scheduled; + bio_list_add(&b->bios, bio); + spin_unlock_irq(&b->lock); + + if (commit_scheduled) + async_commit(b); +} + +/* + * Call this if some urgent work is waiting for the commit to complete. + */ +static void schedule_commit(struct batcher *b) +{ + bool immediate; + + spin_lock_irq(&b->lock); + immediate = !list_empty(&b->work_items) || !bio_list_empty(&b->bios); + b->commit_scheduled = true; + spin_unlock_irq(&b->lock); + + if (immediate) + async_commit(b); +} + +/* + * There are a couple of places where we let a bio run, but want to do some + * work before calling its endio function. We do this by temporarily + * changing the endio fn. + */ +struct dm_hook_info { + bio_end_io_t *bi_end_io; +}; + +static void dm_hook_bio(struct dm_hook_info *h, struct bio *bio, + bio_end_io_t *bi_end_io, void *bi_private) +{ + h->bi_end_io = bio->bi_end_io; + + bio->bi_end_io = bi_end_io; + bio->bi_private = bi_private; +} + +static void dm_unhook_bio(struct dm_hook_info *h, struct bio *bio) +{ + bio->bi_end_io = h->bi_end_io; +} + +/*----------------------------------------------------------------*/ + +#define MIGRATION_POOL_SIZE 128 +#define COMMIT_PERIOD HZ +#define MIGRATION_COUNT_WINDOW 10 + +/* + * The block size of the device holding cache data must be + * between 32KB and 1GB. + */ +#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT) +#define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT) + +enum cache_metadata_mode { + CM_WRITE, /* metadata may be changed */ + CM_READ_ONLY, /* metadata may not be changed */ + CM_FAIL +}; + +enum cache_io_mode { + /* + * Data is written to cached blocks only. These blocks are marked + * dirty. If you lose the cache device you will lose data. + * Potential performance increase for both reads and writes. + */ + CM_IO_WRITEBACK, + + /* + * Data is written to both cache and origin. Blocks are never + * dirty. Potential performance benfit for reads only. + */ + CM_IO_WRITETHROUGH, + + /* + * A degraded mode useful for various cache coherency situations + * (eg, rolling back snapshots). Reads and writes always go to the + * origin. If a write goes to a cached oblock, then the cache + * block is invalidated. + */ + CM_IO_PASSTHROUGH +}; + +struct cache_features { + enum cache_metadata_mode mode; + enum cache_io_mode io_mode; + unsigned int metadata_version; + bool discard_passdown:1; +}; + +struct cache_stats { + atomic_t read_hit; + atomic_t read_miss; + atomic_t write_hit; + atomic_t write_miss; + atomic_t demotion; + atomic_t promotion; + atomic_t writeback; + atomic_t copies_avoided; + atomic_t cache_cell_clash; + atomic_t commit_count; + atomic_t discard_count; +}; + +struct cache { + struct dm_target *ti; + spinlock_t lock; + + /* + * Fields for converting from sectors to blocks. + */ + int sectors_per_block_shift; + sector_t sectors_per_block; + + struct dm_cache_metadata *cmd; + + /* + * Metadata is written to this device. + */ + struct dm_dev *metadata_dev; + + /* + * The slower of the two data devices. Typically a spindle. + */ + struct dm_dev *origin_dev; + + /* + * The faster of the two data devices. Typically an SSD. + */ + struct dm_dev *cache_dev; + + /* + * Size of the origin device in _complete_ blocks and native sectors. + */ + dm_oblock_t origin_blocks; + sector_t origin_sectors; + + /* + * Size of the cache device in blocks. + */ + dm_cblock_t cache_size; + + /* + * Invalidation fields. + */ + spinlock_t invalidation_lock; + struct list_head invalidation_requests; + + sector_t migration_threshold; + wait_queue_head_t migration_wait; + atomic_t nr_allocated_migrations; + + /* + * The number of in flight migrations that are performing + * background io. eg, promotion, writeback. + */ + atomic_t nr_io_migrations; + + struct bio_list deferred_bios; + + struct rw_semaphore quiesce_lock; + + /* + * origin_blocks entries, discarded if set. + */ + dm_dblock_t discard_nr_blocks; + unsigned long *discard_bitset; + uint32_t discard_block_size; /* a power of 2 times sectors per block */ + + /* + * Rather than reconstructing the table line for the status we just + * save it and regurgitate. + */ + unsigned int nr_ctr_args; + const char **ctr_args; + + struct dm_kcopyd_client *copier; + struct work_struct deferred_bio_worker; + struct work_struct migration_worker; + struct workqueue_struct *wq; + struct delayed_work waker; + struct dm_bio_prison_v2 *prison; + + /* + * cache_size entries, dirty if set + */ + unsigned long *dirty_bitset; + atomic_t nr_dirty; + + unsigned int policy_nr_args; + struct dm_cache_policy *policy; + + /* + * Cache features such as write-through. + */ + struct cache_features features; + + struct cache_stats stats; + + bool need_tick_bio:1; + bool sized:1; + bool invalidate:1; + bool commit_requested:1; + bool loaded_mappings:1; + bool loaded_discards:1; + + struct rw_semaphore background_work_lock; + + struct batcher committer; + struct work_struct commit_ws; + + struct dm_io_tracker tracker; + + mempool_t migration_pool; + + struct bio_set bs; +}; + +struct per_bio_data { + bool tick:1; + unsigned int req_nr:2; + struct dm_bio_prison_cell_v2 *cell; + struct dm_hook_info hook_info; + sector_t len; +}; + +struct dm_cache_migration { + struct continuation k; + struct cache *cache; + + struct policy_work *op; + struct bio *overwrite_bio; + struct dm_bio_prison_cell_v2 *cell; + + dm_cblock_t invalidate_cblock; + dm_oblock_t invalidate_oblock; +}; + +/*----------------------------------------------------------------*/ + +static bool writethrough_mode(struct cache *cache) +{ + return cache->features.io_mode == CM_IO_WRITETHROUGH; +} + +static bool writeback_mode(struct cache *cache) +{ + return cache->features.io_mode == CM_IO_WRITEBACK; +} + +static inline bool passthrough_mode(struct cache *cache) +{ + return unlikely(cache->features.io_mode == CM_IO_PASSTHROUGH); +} + +/*----------------------------------------------------------------*/ + +static void wake_deferred_bio_worker(struct cache *cache) +{ + queue_work(cache->wq, &cache->deferred_bio_worker); +} + +static void wake_migration_worker(struct cache *cache) +{ + if (passthrough_mode(cache)) + return; + + queue_work(cache->wq, &cache->migration_worker); +} + +/*----------------------------------------------------------------*/ + +static struct dm_bio_prison_cell_v2 *alloc_prison_cell(struct cache *cache) +{ + return dm_bio_prison_alloc_cell_v2(cache->prison, GFP_NOIO); +} + +static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell_v2 *cell) +{ + dm_bio_prison_free_cell_v2(cache->prison, cell); +} + +static struct dm_cache_migration *alloc_migration(struct cache *cache) +{ + struct dm_cache_migration *mg; + + mg = mempool_alloc(&cache->migration_pool, GFP_NOIO); + + memset(mg, 0, sizeof(*mg)); + + mg->cache = cache; + atomic_inc(&cache->nr_allocated_migrations); + + return mg; +} + +static void free_migration(struct dm_cache_migration *mg) +{ + struct cache *cache = mg->cache; + + if (atomic_dec_and_test(&cache->nr_allocated_migrations)) + wake_up(&cache->migration_wait); + + mempool_free(mg, &cache->migration_pool); +} + +/*----------------------------------------------------------------*/ + +static inline dm_oblock_t oblock_succ(dm_oblock_t b) +{ + return to_oblock(from_oblock(b) + 1ull); +} + +static void build_key(dm_oblock_t begin, dm_oblock_t end, struct dm_cell_key_v2 *key) +{ + key->virtual = 0; + key->dev = 0; + key->block_begin = from_oblock(begin); + key->block_end = from_oblock(end); +} + +/* + * We have two lock levels. Level 0, which is used to prevent WRITEs, and + * level 1 which prevents *both* READs and WRITEs. + */ +#define WRITE_LOCK_LEVEL 0 +#define READ_WRITE_LOCK_LEVEL 1 + +static unsigned int lock_level(struct bio *bio) +{ + return bio_data_dir(bio) == WRITE ? + WRITE_LOCK_LEVEL : + READ_WRITE_LOCK_LEVEL; +} + +/* + *-------------------------------------------------------------- + * Per bio data + *-------------------------------------------------------------- + */ + +static struct per_bio_data *get_per_bio_data(struct bio *bio) +{ + struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data)); + + BUG_ON(!pb); + return pb; +} + +static struct per_bio_data *init_per_bio_data(struct bio *bio) +{ + struct per_bio_data *pb = get_per_bio_data(bio); + + pb->tick = false; + pb->req_nr = dm_bio_get_target_bio_nr(bio); + pb->cell = NULL; + pb->len = 0; + + return pb; +} + +/*----------------------------------------------------------------*/ + +static void defer_bio(struct cache *cache, struct bio *bio) +{ + spin_lock_irq(&cache->lock); + bio_list_add(&cache->deferred_bios, bio); + spin_unlock_irq(&cache->lock); + + wake_deferred_bio_worker(cache); +} + +static void defer_bios(struct cache *cache, struct bio_list *bios) +{ + spin_lock_irq(&cache->lock); + bio_list_merge(&cache->deferred_bios, bios); + bio_list_init(bios); + spin_unlock_irq(&cache->lock); + + wake_deferred_bio_worker(cache); +} + +/*----------------------------------------------------------------*/ + +static bool bio_detain_shared(struct cache *cache, dm_oblock_t oblock, struct bio *bio) +{ + bool r; + struct per_bio_data *pb; + struct dm_cell_key_v2 key; + dm_oblock_t end = to_oblock(from_oblock(oblock) + 1ULL); + struct dm_bio_prison_cell_v2 *cell_prealloc, *cell; + + cell_prealloc = alloc_prison_cell(cache); /* FIXME: allow wait if calling from worker */ + + build_key(oblock, end, &key); + r = dm_cell_get_v2(cache->prison, &key, lock_level(bio), bio, cell_prealloc, &cell); + if (!r) { + /* + * Failed to get the lock. + */ + free_prison_cell(cache, cell_prealloc); + return r; + } + + if (cell != cell_prealloc) + free_prison_cell(cache, cell_prealloc); + + pb = get_per_bio_data(bio); + pb->cell = cell; + + return r; +} + +/*----------------------------------------------------------------*/ + +static bool is_dirty(struct cache *cache, dm_cblock_t b) +{ + return test_bit(from_cblock(b), cache->dirty_bitset); +} + +static void set_dirty(struct cache *cache, dm_cblock_t cblock) +{ + if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) { + atomic_inc(&cache->nr_dirty); + policy_set_dirty(cache->policy, cblock); + } +} + +/* + * These two are called when setting after migrations to force the policy + * and dirty bitset to be in sync. + */ +static void force_set_dirty(struct cache *cache, dm_cblock_t cblock) +{ + if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) + atomic_inc(&cache->nr_dirty); + policy_set_dirty(cache->policy, cblock); +} + +static void force_clear_dirty(struct cache *cache, dm_cblock_t cblock) +{ + if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) { + if (atomic_dec_return(&cache->nr_dirty) == 0) + dm_table_event(cache->ti->table); + } + + policy_clear_dirty(cache->policy, cblock); +} + +/*----------------------------------------------------------------*/ + +static bool block_size_is_power_of_two(struct cache *cache) +{ + return cache->sectors_per_block_shift >= 0; +} + +static dm_block_t block_div(dm_block_t b, uint32_t n) +{ + do_div(b, n); + + return b; +} + +static dm_block_t oblocks_per_dblock(struct cache *cache) +{ + dm_block_t oblocks = cache->discard_block_size; + + if (block_size_is_power_of_two(cache)) + oblocks >>= cache->sectors_per_block_shift; + else + oblocks = block_div(oblocks, cache->sectors_per_block); + + return oblocks; +} + +static dm_dblock_t oblock_to_dblock(struct cache *cache, dm_oblock_t oblock) +{ + return to_dblock(block_div(from_oblock(oblock), + oblocks_per_dblock(cache))); +} + +static void set_discard(struct cache *cache, dm_dblock_t b) +{ + BUG_ON(from_dblock(b) >= from_dblock(cache->discard_nr_blocks)); + atomic_inc(&cache->stats.discard_count); + + spin_lock_irq(&cache->lock); + set_bit(from_dblock(b), cache->discard_bitset); + spin_unlock_irq(&cache->lock); +} + +static void clear_discard(struct cache *cache, dm_dblock_t b) +{ + spin_lock_irq(&cache->lock); + clear_bit(from_dblock(b), cache->discard_bitset); + spin_unlock_irq(&cache->lock); +} + +static bool is_discarded(struct cache *cache, dm_dblock_t b) +{ + int r; + + spin_lock_irq(&cache->lock); + r = test_bit(from_dblock(b), cache->discard_bitset); + spin_unlock_irq(&cache->lock); + + return r; +} + +static bool is_discarded_oblock(struct cache *cache, dm_oblock_t b) +{ + int r; + + spin_lock_irq(&cache->lock); + r = test_bit(from_dblock(oblock_to_dblock(cache, b)), + cache->discard_bitset); + spin_unlock_irq(&cache->lock); + + return r; +} + +/* + * ------------------------------------------------------------- + * Remapping + *-------------------------------------------------------------- + */ +static void remap_to_origin(struct cache *cache, struct bio *bio) +{ + bio_set_dev(bio, cache->origin_dev->bdev); +} + +static void remap_to_cache(struct cache *cache, struct bio *bio, + dm_cblock_t cblock) +{ + sector_t bi_sector = bio->bi_iter.bi_sector; + sector_t block = from_cblock(cblock); + + bio_set_dev(bio, cache->cache_dev->bdev); + if (!block_size_is_power_of_two(cache)) + bio->bi_iter.bi_sector = + (block * cache->sectors_per_block) + + sector_div(bi_sector, cache->sectors_per_block); + else + bio->bi_iter.bi_sector = + (block << cache->sectors_per_block_shift) | + (bi_sector & (cache->sectors_per_block - 1)); +} + +static void check_if_tick_bio_needed(struct cache *cache, struct bio *bio) +{ + struct per_bio_data *pb; + + spin_lock_irq(&cache->lock); + if (cache->need_tick_bio && !op_is_flush(bio->bi_opf) && + bio_op(bio) != REQ_OP_DISCARD) { + pb = get_per_bio_data(bio); + pb->tick = true; + cache->need_tick_bio = false; + } + spin_unlock_irq(&cache->lock); +} + +static void remap_to_origin_clear_discard(struct cache *cache, struct bio *bio, + dm_oblock_t oblock) +{ + // FIXME: check_if_tick_bio_needed() is called way too much through this interface + check_if_tick_bio_needed(cache, bio); + remap_to_origin(cache, bio); + if (bio_data_dir(bio) == WRITE) + clear_discard(cache, oblock_to_dblock(cache, oblock)); +} + +static void remap_to_cache_dirty(struct cache *cache, struct bio *bio, + dm_oblock_t oblock, dm_cblock_t cblock) +{ + check_if_tick_bio_needed(cache, bio); + remap_to_cache(cache, bio, cblock); + if (bio_data_dir(bio) == WRITE) { + set_dirty(cache, cblock); + clear_discard(cache, oblock_to_dblock(cache, oblock)); + } +} + +static dm_oblock_t get_bio_block(struct cache *cache, struct bio *bio) +{ + sector_t block_nr = bio->bi_iter.bi_sector; + + if (!block_size_is_power_of_two(cache)) + (void) sector_div(block_nr, cache->sectors_per_block); + else + block_nr >>= cache->sectors_per_block_shift; + + return to_oblock(block_nr); +} + +static bool accountable_bio(struct cache *cache, struct bio *bio) +{ + return bio_op(bio) != REQ_OP_DISCARD; +} + +static void accounted_begin(struct cache *cache, struct bio *bio) +{ + struct per_bio_data *pb; + + if (accountable_bio(cache, bio)) { + pb = get_per_bio_data(bio); + pb->len = bio_sectors(bio); + dm_iot_io_begin(&cache->tracker, pb->len); + } +} + +static void accounted_complete(struct cache *cache, struct bio *bio) +{ + struct per_bio_data *pb = get_per_bio_data(bio); + + dm_iot_io_end(&cache->tracker, pb->len); +} + +static void accounted_request(struct cache *cache, struct bio *bio) +{ + accounted_begin(cache, bio); + dm_submit_bio_remap(bio, NULL); +} + +static void issue_op(struct bio *bio, void *context) +{ + struct cache *cache = context; + + accounted_request(cache, bio); +} + +/* + * When running in writethrough mode we need to send writes to clean blocks + * to both the cache and origin devices. Clone the bio and send them in parallel. + */ +static void remap_to_origin_and_cache(struct cache *cache, struct bio *bio, + dm_oblock_t oblock, dm_cblock_t cblock) +{ + struct bio *origin_bio = bio_alloc_clone(cache->origin_dev->bdev, bio, + GFP_NOIO, &cache->bs); + + BUG_ON(!origin_bio); + + bio_chain(origin_bio, bio); + + if (bio_data_dir(origin_bio) == WRITE) + clear_discard(cache, oblock_to_dblock(cache, oblock)); + submit_bio(origin_bio); + + remap_to_cache(cache, bio, cblock); +} + +/* + *-------------------------------------------------------------- + * Failure modes + *-------------------------------------------------------------- + */ +static enum cache_metadata_mode get_cache_mode(struct cache *cache) +{ + return cache->features.mode; +} + +static const char *cache_device_name(struct cache *cache) +{ + return dm_table_device_name(cache->ti->table); +} + +static void notify_mode_switch(struct cache *cache, enum cache_metadata_mode mode) +{ + static const char *descs[] = { + "write", + "read-only", + "fail" + }; + + dm_table_event(cache->ti->table); + DMINFO("%s: switching cache to %s mode", + cache_device_name(cache), descs[(int)mode]); +} + +static void set_cache_mode(struct cache *cache, enum cache_metadata_mode new_mode) +{ + bool needs_check; + enum cache_metadata_mode old_mode = get_cache_mode(cache); + + if (dm_cache_metadata_needs_check(cache->cmd, &needs_check)) { + DMERR("%s: unable to read needs_check flag, setting failure mode.", + cache_device_name(cache)); + new_mode = CM_FAIL; + } + + if (new_mode == CM_WRITE && needs_check) { + DMERR("%s: unable to switch cache to write mode until repaired.", + cache_device_name(cache)); + if (old_mode != new_mode) + new_mode = old_mode; + else + new_mode = CM_READ_ONLY; + } + + /* Never move out of fail mode */ + if (old_mode == CM_FAIL) + new_mode = CM_FAIL; + + switch (new_mode) { + case CM_FAIL: + case CM_READ_ONLY: + dm_cache_metadata_set_read_only(cache->cmd); + break; + + case CM_WRITE: + dm_cache_metadata_set_read_write(cache->cmd); + break; + } + + cache->features.mode = new_mode; + + if (new_mode != old_mode) + notify_mode_switch(cache, new_mode); +} + +static void abort_transaction(struct cache *cache) +{ + const char *dev_name = cache_device_name(cache); + + if (get_cache_mode(cache) >= CM_READ_ONLY) + return; + + DMERR_LIMIT("%s: aborting current metadata transaction", dev_name); + if (dm_cache_metadata_abort(cache->cmd)) { + DMERR("%s: failed to abort metadata transaction", dev_name); + set_cache_mode(cache, CM_FAIL); + } + + if (dm_cache_metadata_set_needs_check(cache->cmd)) { + DMERR("%s: failed to set 'needs_check' flag in metadata", dev_name); + set_cache_mode(cache, CM_FAIL); + } +} + +static void metadata_operation_failed(struct cache *cache, const char *op, int r) +{ + DMERR_LIMIT("%s: metadata operation '%s' failed: error = %d", + cache_device_name(cache), op, r); + abort_transaction(cache); + set_cache_mode(cache, CM_READ_ONLY); +} + +/*----------------------------------------------------------------*/ + +static void load_stats(struct cache *cache) +{ + struct dm_cache_statistics stats; + + dm_cache_metadata_get_stats(cache->cmd, &stats); + atomic_set(&cache->stats.read_hit, stats.read_hits); + atomic_set(&cache->stats.read_miss, stats.read_misses); + atomic_set(&cache->stats.write_hit, stats.write_hits); + atomic_set(&cache->stats.write_miss, stats.write_misses); +} + +static void save_stats(struct cache *cache) +{ + struct dm_cache_statistics stats; + + if (get_cache_mode(cache) >= CM_READ_ONLY) + return; + + stats.read_hits = atomic_read(&cache->stats.read_hit); + stats.read_misses = atomic_read(&cache->stats.read_miss); + stats.write_hits = atomic_read(&cache->stats.write_hit); + stats.write_misses = atomic_read(&cache->stats.write_miss); + + dm_cache_metadata_set_stats(cache->cmd, &stats); +} + +static void update_stats(struct cache_stats *stats, enum policy_operation op) +{ + switch (op) { + case POLICY_PROMOTE: + atomic_inc(&stats->promotion); + break; + + case POLICY_DEMOTE: + atomic_inc(&stats->demotion); + break; + + case POLICY_WRITEBACK: + atomic_inc(&stats->writeback); + break; + } +} + +/* + *--------------------------------------------------------------------- + * Migration processing + * + * Migration covers moving data from the origin device to the cache, or + * vice versa. + *--------------------------------------------------------------------- + */ +static void inc_io_migrations(struct cache *cache) +{ + atomic_inc(&cache->nr_io_migrations); +} + +static void dec_io_migrations(struct cache *cache) +{ + atomic_dec(&cache->nr_io_migrations); +} + +static bool discard_or_flush(struct bio *bio) +{ + return bio_op(bio) == REQ_OP_DISCARD || op_is_flush(bio->bi_opf); +} + +static void calc_discard_block_range(struct cache *cache, struct bio *bio, + dm_dblock_t *b, dm_dblock_t *e) +{ + sector_t sb = bio->bi_iter.bi_sector; + sector_t se = bio_end_sector(bio); + + *b = to_dblock(dm_sector_div_up(sb, cache->discard_block_size)); + + if (se - sb < cache->discard_block_size) + *e = *b; + else + *e = to_dblock(block_div(se, cache->discard_block_size)); +} + +/*----------------------------------------------------------------*/ + +static void prevent_background_work(struct cache *cache) +{ + lockdep_off(); + down_write(&cache->background_work_lock); + lockdep_on(); +} + +static void allow_background_work(struct cache *cache) +{ + lockdep_off(); + up_write(&cache->background_work_lock); + lockdep_on(); +} + +static bool background_work_begin(struct cache *cache) +{ + bool r; + + lockdep_off(); + r = down_read_trylock(&cache->background_work_lock); + lockdep_on(); + + return r; +} + +static void background_work_end(struct cache *cache) +{ + lockdep_off(); + up_read(&cache->background_work_lock); + lockdep_on(); +} + +/*----------------------------------------------------------------*/ + +static bool bio_writes_complete_block(struct cache *cache, struct bio *bio) +{ + return (bio_data_dir(bio) == WRITE) && + (bio->bi_iter.bi_size == (cache->sectors_per_block << SECTOR_SHIFT)); +} + +static bool optimisable_bio(struct cache *cache, struct bio *bio, dm_oblock_t block) +{ + return writeback_mode(cache) && + (is_discarded_oblock(cache, block) || bio_writes_complete_block(cache, bio)); +} + +static void quiesce(struct dm_cache_migration *mg, + void (*continuation)(struct work_struct *)) +{ + init_continuation(&mg->k, continuation); + dm_cell_quiesce_v2(mg->cache->prison, mg->cell, &mg->k.ws); +} + +static struct dm_cache_migration *ws_to_mg(struct work_struct *ws) +{ + struct continuation *k = container_of(ws, struct continuation, ws); + + return container_of(k, struct dm_cache_migration, k); +} + +static void copy_complete(int read_err, unsigned long write_err, void *context) +{ + struct dm_cache_migration *mg = container_of(context, struct dm_cache_migration, k); + + if (read_err || write_err) + mg->k.input = BLK_STS_IOERR; + + queue_continuation(mg->cache->wq, &mg->k); +} + +static void copy(struct dm_cache_migration *mg, bool promote) +{ + struct dm_io_region o_region, c_region; + struct cache *cache = mg->cache; + + o_region.bdev = cache->origin_dev->bdev; + o_region.sector = from_oblock(mg->op->oblock) * cache->sectors_per_block; + o_region.count = cache->sectors_per_block; + + c_region.bdev = cache->cache_dev->bdev; + c_region.sector = from_cblock(mg->op->cblock) * cache->sectors_per_block; + c_region.count = cache->sectors_per_block; + + if (promote) + dm_kcopyd_copy(cache->copier, &o_region, 1, &c_region, 0, copy_complete, &mg->k); + else + dm_kcopyd_copy(cache->copier, &c_region, 1, &o_region, 0, copy_complete, &mg->k); +} + +static void bio_drop_shared_lock(struct cache *cache, struct bio *bio) +{ + struct per_bio_data *pb = get_per_bio_data(bio); + + if (pb->cell && dm_cell_put_v2(cache->prison, pb->cell)) + free_prison_cell(cache, pb->cell); + pb->cell = NULL; +} + +static void overwrite_endio(struct bio *bio) +{ + struct dm_cache_migration *mg = bio->bi_private; + struct cache *cache = mg->cache; + struct per_bio_data *pb = get_per_bio_data(bio); + + dm_unhook_bio(&pb->hook_info, bio); + + if (bio->bi_status) + mg->k.input = bio->bi_status; + + queue_continuation(cache->wq, &mg->k); +} + +static void overwrite(struct dm_cache_migration *mg, + void (*continuation)(struct work_struct *)) +{ + struct bio *bio = mg->overwrite_bio; + struct per_bio_data *pb = get_per_bio_data(bio); + + dm_hook_bio(&pb->hook_info, bio, overwrite_endio, mg); + + /* + * The overwrite bio is part of the copy operation, as such it does + * not set/clear discard or dirty flags. + */ + if (mg->op->op == POLICY_PROMOTE) + remap_to_cache(mg->cache, bio, mg->op->cblock); + else + remap_to_origin(mg->cache, bio); + + init_continuation(&mg->k, continuation); + accounted_request(mg->cache, bio); +} + +/* + * Migration steps: + * + * 1) exclusive lock preventing WRITEs + * 2) quiesce + * 3) copy or issue overwrite bio + * 4) upgrade to exclusive lock preventing READs and WRITEs + * 5) quiesce + * 6) update metadata and commit + * 7) unlock + */ +static void mg_complete(struct dm_cache_migration *mg, bool success) +{ + struct bio_list bios; + struct cache *cache = mg->cache; + struct policy_work *op = mg->op; + dm_cblock_t cblock = op->cblock; + + if (success) + update_stats(&cache->stats, op->op); + + switch (op->op) { + case POLICY_PROMOTE: + clear_discard(cache, oblock_to_dblock(cache, op->oblock)); + policy_complete_background_work(cache->policy, op, success); + + if (mg->overwrite_bio) { + if (success) + force_set_dirty(cache, cblock); + else if (mg->k.input) + mg->overwrite_bio->bi_status = mg->k.input; + else + mg->overwrite_bio->bi_status = BLK_STS_IOERR; + bio_endio(mg->overwrite_bio); + } else { + if (success) + force_clear_dirty(cache, cblock); + dec_io_migrations(cache); + } + break; + + case POLICY_DEMOTE: + /* + * We clear dirty here to update the nr_dirty counter. + */ + if (success) + force_clear_dirty(cache, cblock); + policy_complete_background_work(cache->policy, op, success); + dec_io_migrations(cache); + break; + + case POLICY_WRITEBACK: + if (success) + force_clear_dirty(cache, cblock); + policy_complete_background_work(cache->policy, op, success); + dec_io_migrations(cache); + break; + } + + bio_list_init(&bios); + if (mg->cell) { + if (dm_cell_unlock_v2(cache->prison, mg->cell, &bios)) + free_prison_cell(cache, mg->cell); + } + + free_migration(mg); + defer_bios(cache, &bios); + wake_migration_worker(cache); + + background_work_end(cache); +} + +static void mg_success(struct work_struct *ws) +{ + struct dm_cache_migration *mg = ws_to_mg(ws); + + mg_complete(mg, mg->k.input == 0); +} + +static void mg_update_metadata(struct work_struct *ws) +{ + int r; + struct dm_cache_migration *mg = ws_to_mg(ws); + struct cache *cache = mg->cache; + struct policy_work *op = mg->op; + + switch (op->op) { + case POLICY_PROMOTE: + r = dm_cache_insert_mapping(cache->cmd, op->cblock, op->oblock); + if (r) { + DMERR_LIMIT("%s: migration failed; couldn't insert mapping", + cache_device_name(cache)); + metadata_operation_failed(cache, "dm_cache_insert_mapping", r); + + mg_complete(mg, false); + return; + } + mg_complete(mg, true); + break; + + case POLICY_DEMOTE: + r = dm_cache_remove_mapping(cache->cmd, op->cblock); + if (r) { + DMERR_LIMIT("%s: migration failed; couldn't update on disk metadata", + cache_device_name(cache)); + metadata_operation_failed(cache, "dm_cache_remove_mapping", r); + + mg_complete(mg, false); + return; + } + + /* + * It would be nice if we only had to commit when a REQ_FLUSH + * comes through. But there's one scenario that we have to + * look out for: + * + * - vblock x in a cache block + * - domotion occurs + * - cache block gets reallocated and over written + * - crash + * + * When we recover, because there was no commit the cache will + * rollback to having the data for vblock x in the cache block. + * But the cache block has since been overwritten, so it'll end + * up pointing to data that was never in 'x' during the history + * of the device. + * + * To avoid this issue we require a commit as part of the + * demotion operation. + */ + init_continuation(&mg->k, mg_success); + continue_after_commit(&cache->committer, &mg->k); + schedule_commit(&cache->committer); + break; + + case POLICY_WRITEBACK: + mg_complete(mg, true); + break; + } +} + +static void mg_update_metadata_after_copy(struct work_struct *ws) +{ + struct dm_cache_migration *mg = ws_to_mg(ws); + + /* + * Did the copy succeed? + */ + if (mg->k.input) + mg_complete(mg, false); + else + mg_update_metadata(ws); +} + +static void mg_upgrade_lock(struct work_struct *ws) +{ + int r; + struct dm_cache_migration *mg = ws_to_mg(ws); + + /* + * Did the copy succeed? + */ + if (mg->k.input) + mg_complete(mg, false); + + else { + /* + * Now we want the lock to prevent both reads and writes. + */ + r = dm_cell_lock_promote_v2(mg->cache->prison, mg->cell, + READ_WRITE_LOCK_LEVEL); + if (r < 0) + mg_complete(mg, false); + + else if (r) + quiesce(mg, mg_update_metadata); + + else + mg_update_metadata(ws); + } +} + +static void mg_full_copy(struct work_struct *ws) +{ + struct dm_cache_migration *mg = ws_to_mg(ws); + struct cache *cache = mg->cache; + struct policy_work *op = mg->op; + bool is_policy_promote = (op->op == POLICY_PROMOTE); + + if ((!is_policy_promote && !is_dirty(cache, op->cblock)) || + is_discarded_oblock(cache, op->oblock)) { + mg_upgrade_lock(ws); + return; + } + + init_continuation(&mg->k, mg_upgrade_lock); + copy(mg, is_policy_promote); +} + +static void mg_copy(struct work_struct *ws) +{ + struct dm_cache_migration *mg = ws_to_mg(ws); + + if (mg->overwrite_bio) { + /* + * No exclusive lock was held when we last checked if the bio + * was optimisable. So we have to check again in case things + * have changed (eg, the block may no longer be discarded). + */ + if (!optimisable_bio(mg->cache, mg->overwrite_bio, mg->op->oblock)) { + /* + * Fallback to a real full copy after doing some tidying up. + */ + bool rb = bio_detain_shared(mg->cache, mg->op->oblock, mg->overwrite_bio); + + BUG_ON(rb); /* An exclussive lock must _not_ be held for this block */ + mg->overwrite_bio = NULL; + inc_io_migrations(mg->cache); + mg_full_copy(ws); + return; + } + + /* + * It's safe to do this here, even though it's new data + * because all IO has been locked out of the block. + * + * mg_lock_writes() already took READ_WRITE_LOCK_LEVEL + * so _not_ using mg_upgrade_lock() as continutation. + */ + overwrite(mg, mg_update_metadata_after_copy); + + } else + mg_full_copy(ws); +} + +static int mg_lock_writes(struct dm_cache_migration *mg) +{ + int r; + struct dm_cell_key_v2 key; + struct cache *cache = mg->cache; + struct dm_bio_prison_cell_v2 *prealloc; + + prealloc = alloc_prison_cell(cache); + + /* + * Prevent writes to the block, but allow reads to continue. + * Unless we're using an overwrite bio, in which case we lock + * everything. + */ + build_key(mg->op->oblock, oblock_succ(mg->op->oblock), &key); + r = dm_cell_lock_v2(cache->prison, &key, + mg->overwrite_bio ? READ_WRITE_LOCK_LEVEL : WRITE_LOCK_LEVEL, + prealloc, &mg->cell); + if (r < 0) { + free_prison_cell(cache, prealloc); + mg_complete(mg, false); + return r; + } + + if (mg->cell != prealloc) + free_prison_cell(cache, prealloc); + + if (r == 0) + mg_copy(&mg->k.ws); + else + quiesce(mg, mg_copy); + + return 0; +} + +static int mg_start(struct cache *cache, struct policy_work *op, struct bio *bio) +{ + struct dm_cache_migration *mg; + + if (!background_work_begin(cache)) { + policy_complete_background_work(cache->policy, op, false); + return -EPERM; + } + + mg = alloc_migration(cache); + + mg->op = op; + mg->overwrite_bio = bio; + + if (!bio) + inc_io_migrations(cache); + + return mg_lock_writes(mg); +} + +/* + *-------------------------------------------------------------- + * invalidation processing + *-------------------------------------------------------------- + */ + +static void invalidate_complete(struct dm_cache_migration *mg, bool success) +{ + struct bio_list bios; + struct cache *cache = mg->cache; + + bio_list_init(&bios); + if (dm_cell_unlock_v2(cache->prison, mg->cell, &bios)) + free_prison_cell(cache, mg->cell); + + if (!success && mg->overwrite_bio) + bio_io_error(mg->overwrite_bio); + + free_migration(mg); + defer_bios(cache, &bios); + + background_work_end(cache); +} + +static void invalidate_completed(struct work_struct *ws) +{ + struct dm_cache_migration *mg = ws_to_mg(ws); + + invalidate_complete(mg, !mg->k.input); +} + +static int invalidate_cblock(struct cache *cache, dm_cblock_t cblock) +{ + int r; + + r = policy_invalidate_mapping(cache->policy, cblock); + if (!r) { + r = dm_cache_remove_mapping(cache->cmd, cblock); + if (r) { + DMERR_LIMIT("%s: invalidation failed; couldn't update on disk metadata", + cache_device_name(cache)); + metadata_operation_failed(cache, "dm_cache_remove_mapping", r); + } + + } else if (r == -ENODATA) { + /* + * Harmless, already unmapped. + */ + r = 0; + + } else + DMERR("%s: policy_invalidate_mapping failed", cache_device_name(cache)); + + return r; +} + +static void invalidate_remove(struct work_struct *ws) +{ + int r; + struct dm_cache_migration *mg = ws_to_mg(ws); + struct cache *cache = mg->cache; + + r = invalidate_cblock(cache, mg->invalidate_cblock); + if (r) { + invalidate_complete(mg, false); + return; + } + + init_continuation(&mg->k, invalidate_completed); + continue_after_commit(&cache->committer, &mg->k); + remap_to_origin_clear_discard(cache, mg->overwrite_bio, mg->invalidate_oblock); + mg->overwrite_bio = NULL; + schedule_commit(&cache->committer); +} + +static int invalidate_lock(struct dm_cache_migration *mg) +{ + int r; + struct dm_cell_key_v2 key; + struct cache *cache = mg->cache; + struct dm_bio_prison_cell_v2 *prealloc; + + prealloc = alloc_prison_cell(cache); + + build_key(mg->invalidate_oblock, oblock_succ(mg->invalidate_oblock), &key); + r = dm_cell_lock_v2(cache->prison, &key, + READ_WRITE_LOCK_LEVEL, prealloc, &mg->cell); + if (r < 0) { + free_prison_cell(cache, prealloc); + invalidate_complete(mg, false); + return r; + } + + if (mg->cell != prealloc) + free_prison_cell(cache, prealloc); + + if (r) + quiesce(mg, invalidate_remove); + + else { + /* + * We can't call invalidate_remove() directly here because we + * might still be in request context. + */ + init_continuation(&mg->k, invalidate_remove); + queue_work(cache->wq, &mg->k.ws); + } + + return 0; +} + +static int invalidate_start(struct cache *cache, dm_cblock_t cblock, + dm_oblock_t oblock, struct bio *bio) +{ + struct dm_cache_migration *mg; + + if (!background_work_begin(cache)) + return -EPERM; + + mg = alloc_migration(cache); + + mg->overwrite_bio = bio; + mg->invalidate_cblock = cblock; + mg->invalidate_oblock = oblock; + + return invalidate_lock(mg); +} + +/* + *-------------------------------------------------------------- + * bio processing + *-------------------------------------------------------------- + */ + +enum busy { + IDLE, + BUSY +}; + +static enum busy spare_migration_bandwidth(struct cache *cache) +{ + bool idle = dm_iot_idle_for(&cache->tracker, HZ); + sector_t current_volume = (atomic_read(&cache->nr_io_migrations) + 1) * + cache->sectors_per_block; + + if (idle && current_volume <= cache->migration_threshold) + return IDLE; + else + return BUSY; +} + +static void inc_hit_counter(struct cache *cache, struct bio *bio) +{ + atomic_inc(bio_data_dir(bio) == READ ? + &cache->stats.read_hit : &cache->stats.write_hit); +} + +static void inc_miss_counter(struct cache *cache, struct bio *bio) +{ + atomic_inc(bio_data_dir(bio) == READ ? + &cache->stats.read_miss : &cache->stats.write_miss); +} + +/*----------------------------------------------------------------*/ + +static int map_bio(struct cache *cache, struct bio *bio, dm_oblock_t block, + bool *commit_needed) +{ + int r, data_dir; + bool rb, background_queued; + dm_cblock_t cblock; + + *commit_needed = false; + + rb = bio_detain_shared(cache, block, bio); + if (!rb) { + /* + * An exclusive lock is held for this block, so we have to + * wait. We set the commit_needed flag so the current + * transaction will be committed asap, allowing this lock + * to be dropped. + */ + *commit_needed = true; + return DM_MAPIO_SUBMITTED; + } + + data_dir = bio_data_dir(bio); + + if (optimisable_bio(cache, bio, block)) { + struct policy_work *op = NULL; + + r = policy_lookup_with_work(cache->policy, block, &cblock, data_dir, true, &op); + if (unlikely(r && r != -ENOENT)) { + DMERR_LIMIT("%s: policy_lookup_with_work() failed with r = %d", + cache_device_name(cache), r); + bio_io_error(bio); + return DM_MAPIO_SUBMITTED; + } + + if (r == -ENOENT && op) { + bio_drop_shared_lock(cache, bio); + BUG_ON(op->op != POLICY_PROMOTE); + mg_start(cache, op, bio); + return DM_MAPIO_SUBMITTED; + } + } else { + r = policy_lookup(cache->policy, block, &cblock, data_dir, false, &background_queued); + if (unlikely(r && r != -ENOENT)) { + DMERR_LIMIT("%s: policy_lookup() failed with r = %d", + cache_device_name(cache), r); + bio_io_error(bio); + return DM_MAPIO_SUBMITTED; + } + + if (background_queued) + wake_migration_worker(cache); + } + + if (r == -ENOENT) { + struct per_bio_data *pb = get_per_bio_data(bio); + + /* + * Miss. + */ + inc_miss_counter(cache, bio); + if (pb->req_nr == 0) { + accounted_begin(cache, bio); + remap_to_origin_clear_discard(cache, bio, block); + } else { + /* + * This is a duplicate writethrough io that is no + * longer needed because the block has been demoted. + */ + bio_endio(bio); + return DM_MAPIO_SUBMITTED; + } + } else { + /* + * Hit. + */ + inc_hit_counter(cache, bio); + + /* + * Passthrough always maps to the origin, invalidating any + * cache blocks that are written to. + */ + if (passthrough_mode(cache)) { + if (bio_data_dir(bio) == WRITE) { + bio_drop_shared_lock(cache, bio); + atomic_inc(&cache->stats.demotion); + invalidate_start(cache, cblock, block, bio); + } else + remap_to_origin_clear_discard(cache, bio, block); + } else { + if (bio_data_dir(bio) == WRITE && writethrough_mode(cache) && + !is_dirty(cache, cblock)) { + remap_to_origin_and_cache(cache, bio, block, cblock); + accounted_begin(cache, bio); + } else + remap_to_cache_dirty(cache, bio, block, cblock); + } + } + + /* + * dm core turns FUA requests into a separate payload and FLUSH req. + */ + if (bio->bi_opf & REQ_FUA) { + /* + * issue_after_commit will call accounted_begin a second time. So + * we call accounted_complete() to avoid double accounting. + */ + accounted_complete(cache, bio); + issue_after_commit(&cache->committer, bio); + *commit_needed = true; + return DM_MAPIO_SUBMITTED; + } + + return DM_MAPIO_REMAPPED; +} + +static bool process_bio(struct cache *cache, struct bio *bio) +{ + bool commit_needed; + + if (map_bio(cache, bio, get_bio_block(cache, bio), &commit_needed) == DM_MAPIO_REMAPPED) + dm_submit_bio_remap(bio, NULL); + + return commit_needed; +} + +/* + * A non-zero return indicates read_only or fail_io mode. + */ +static int commit(struct cache *cache, bool clean_shutdown) +{ + int r; + + if (get_cache_mode(cache) >= CM_READ_ONLY) + return -EINVAL; + + atomic_inc(&cache->stats.commit_count); + r = dm_cache_commit(cache->cmd, clean_shutdown); + if (r) + metadata_operation_failed(cache, "dm_cache_commit", r); + + return r; +} + +/* + * Used by the batcher. + */ +static blk_status_t commit_op(void *context) +{ + struct cache *cache = context; + + if (dm_cache_changed_this_transaction(cache->cmd)) + return errno_to_blk_status(commit(cache, false)); + + return 0; +} + +/*----------------------------------------------------------------*/ + +static bool process_flush_bio(struct cache *cache, struct bio *bio) +{ + struct per_bio_data *pb = get_per_bio_data(bio); + + if (!pb->req_nr) + remap_to_origin(cache, bio); + else + remap_to_cache(cache, bio, 0); + + issue_after_commit(&cache->committer, bio); + return true; +} + +static bool process_discard_bio(struct cache *cache, struct bio *bio) +{ + dm_dblock_t b, e; + + /* + * FIXME: do we need to lock the region? Or can we just assume the + * user wont be so foolish as to issue discard concurrently with + * other IO? + */ + calc_discard_block_range(cache, bio, &b, &e); + while (b != e) { + set_discard(cache, b); + b = to_dblock(from_dblock(b) + 1); + } + + if (cache->features.discard_passdown) { + remap_to_origin(cache, bio); + dm_submit_bio_remap(bio, NULL); + } else + bio_endio(bio); + + return false; +} + +static void process_deferred_bios(struct work_struct *ws) +{ + struct cache *cache = container_of(ws, struct cache, deferred_bio_worker); + + bool commit_needed = false; + struct bio_list bios; + struct bio *bio; + + bio_list_init(&bios); + + spin_lock_irq(&cache->lock); + bio_list_merge(&bios, &cache->deferred_bios); + bio_list_init(&cache->deferred_bios); + spin_unlock_irq(&cache->lock); + + while ((bio = bio_list_pop(&bios))) { + if (bio->bi_opf & REQ_PREFLUSH) + commit_needed = process_flush_bio(cache, bio) || commit_needed; + + else if (bio_op(bio) == REQ_OP_DISCARD) + commit_needed = process_discard_bio(cache, bio) || commit_needed; + + else + commit_needed = process_bio(cache, bio) || commit_needed; + cond_resched(); + } + + if (commit_needed) + schedule_commit(&cache->committer); +} + +/* + *-------------------------------------------------------------- + * Main worker loop + *-------------------------------------------------------------- + */ +static void requeue_deferred_bios(struct cache *cache) +{ + struct bio *bio; + struct bio_list bios; + + bio_list_init(&bios); + bio_list_merge(&bios, &cache->deferred_bios); + bio_list_init(&cache->deferred_bios); + + while ((bio = bio_list_pop(&bios))) { + bio->bi_status = BLK_STS_DM_REQUEUE; + bio_endio(bio); + cond_resched(); + } +} + +/* + * We want to commit periodically so that not too much + * unwritten metadata builds up. + */ +static void do_waker(struct work_struct *ws) +{ + struct cache *cache = container_of(to_delayed_work(ws), struct cache, waker); + + policy_tick(cache->policy, true); + wake_migration_worker(cache); + schedule_commit(&cache->committer); + queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD); +} + +static void check_migrations(struct work_struct *ws) +{ + int r; + struct policy_work *op; + struct cache *cache = container_of(ws, struct cache, migration_worker); + enum busy b; + + for (;;) { + b = spare_migration_bandwidth(cache); + + r = policy_get_background_work(cache->policy, b == IDLE, &op); + if (r == -ENODATA) + break; + + if (r) { + DMERR_LIMIT("%s: policy_background_work failed", + cache_device_name(cache)); + break; + } + + r = mg_start(cache, op, NULL); + if (r) + break; + + cond_resched(); + } +} + +/* + *-------------------------------------------------------------- + * Target methods + *-------------------------------------------------------------- + */ + +/* + * This function gets called on the error paths of the constructor, so we + * have to cope with a partially initialised struct. + */ +static void destroy(struct cache *cache) +{ + unsigned int i; + + mempool_exit(&cache->migration_pool); + + if (cache->prison) + dm_bio_prison_destroy_v2(cache->prison); + + cancel_delayed_work_sync(&cache->waker); + if (cache->wq) + destroy_workqueue(cache->wq); + + if (cache->dirty_bitset) + free_bitset(cache->dirty_bitset); + + if (cache->discard_bitset) + free_bitset(cache->discard_bitset); + + if (cache->copier) + dm_kcopyd_client_destroy(cache->copier); + + if (cache->cmd) + dm_cache_metadata_close(cache->cmd); + + if (cache->metadata_dev) + dm_put_device(cache->ti, cache->metadata_dev); + + if (cache->origin_dev) + dm_put_device(cache->ti, cache->origin_dev); + + if (cache->cache_dev) + dm_put_device(cache->ti, cache->cache_dev); + + if (cache->policy) + dm_cache_policy_destroy(cache->policy); + + for (i = 0; i < cache->nr_ctr_args ; i++) + kfree(cache->ctr_args[i]); + kfree(cache->ctr_args); + + bioset_exit(&cache->bs); + + kfree(cache); +} + +static void cache_dtr(struct dm_target *ti) +{ + struct cache *cache = ti->private; + + destroy(cache); +} + +static sector_t get_dev_size(struct dm_dev *dev) +{ + return bdev_nr_sectors(dev->bdev); +} + +/*----------------------------------------------------------------*/ + +/* + * Construct a cache device mapping. + * + * cache <metadata dev> <cache dev> <origin dev> <block size> + * <#feature args> [<feature arg>]* + * <policy> <#policy args> [<policy arg>]* + * + * metadata dev : fast device holding the persistent metadata + * cache dev : fast device holding cached data blocks + * origin dev : slow device holding original data blocks + * block size : cache unit size in sectors + * + * #feature args : number of feature arguments passed + * feature args : writethrough. (The default is writeback.) + * + * policy : the replacement policy to use + * #policy args : an even number of policy arguments corresponding + * to key/value pairs passed to the policy + * policy args : key/value pairs passed to the policy + * E.g. 'sequential_threshold 1024' + * See cache-policies.txt for details. + * + * Optional feature arguments are: + * writethrough : write through caching that prohibits cache block + * content from being different from origin block content. + * Without this argument, the default behaviour is to write + * back cache block contents later for performance reasons, + * so they may differ from the corresponding origin blocks. + */ +struct cache_args { + struct dm_target *ti; + + struct dm_dev *metadata_dev; + + struct dm_dev *cache_dev; + sector_t cache_sectors; + + struct dm_dev *origin_dev; + sector_t origin_sectors; + + uint32_t block_size; + + const char *policy_name; + int policy_argc; + const char **policy_argv; + + struct cache_features features; +}; + +static void destroy_cache_args(struct cache_args *ca) +{ + if (ca->metadata_dev) + dm_put_device(ca->ti, ca->metadata_dev); + + if (ca->cache_dev) + dm_put_device(ca->ti, ca->cache_dev); + + if (ca->origin_dev) + dm_put_device(ca->ti, ca->origin_dev); + + kfree(ca); +} + +static bool at_least_one_arg(struct dm_arg_set *as, char **error) +{ + if (!as->argc) { + *error = "Insufficient args"; + return false; + } + + return true; +} + +static int parse_metadata_dev(struct cache_args *ca, struct dm_arg_set *as, + char **error) +{ + int r; + sector_t metadata_dev_size; + + if (!at_least_one_arg(as, error)) + return -EINVAL; + + r = dm_get_device(ca->ti, dm_shift_arg(as), + BLK_OPEN_READ | BLK_OPEN_WRITE, &ca->metadata_dev); + if (r) { + *error = "Error opening metadata device"; + return r; + } + + metadata_dev_size = get_dev_size(ca->metadata_dev); + if (metadata_dev_size > DM_CACHE_METADATA_MAX_SECTORS_WARNING) + DMWARN("Metadata device %pg is larger than %u sectors: excess space will not be used.", + ca->metadata_dev->bdev, THIN_METADATA_MAX_SECTORS); + + return 0; +} + +static int parse_cache_dev(struct cache_args *ca, struct dm_arg_set *as, + char **error) +{ + int r; + + if (!at_least_one_arg(as, error)) + return -EINVAL; + + r = dm_get_device(ca->ti, dm_shift_arg(as), + BLK_OPEN_READ | BLK_OPEN_WRITE, &ca->cache_dev); + if (r) { + *error = "Error opening cache device"; + return r; + } + ca->cache_sectors = get_dev_size(ca->cache_dev); + + return 0; +} + +static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as, + char **error) +{ + int r; + + if (!at_least_one_arg(as, error)) + return -EINVAL; + + r = dm_get_device(ca->ti, dm_shift_arg(as), + BLK_OPEN_READ | BLK_OPEN_WRITE, &ca->origin_dev); + if (r) { + *error = "Error opening origin device"; + return r; + } + + ca->origin_sectors = get_dev_size(ca->origin_dev); + if (ca->ti->len > ca->origin_sectors) { + *error = "Device size larger than cached device"; + return -EINVAL; + } + + return 0; +} + +static int parse_block_size(struct cache_args *ca, struct dm_arg_set *as, + char **error) +{ + unsigned long block_size; + + if (!at_least_one_arg(as, error)) + return -EINVAL; + + if (kstrtoul(dm_shift_arg(as), 10, &block_size) || !block_size || + block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS || + block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS || + block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) { + *error = "Invalid data block size"; + return -EINVAL; + } + + if (block_size > ca->cache_sectors) { + *error = "Data block size is larger than the cache device"; + return -EINVAL; + } + + ca->block_size = block_size; + + return 0; +} + +static void init_features(struct cache_features *cf) +{ + cf->mode = CM_WRITE; + cf->io_mode = CM_IO_WRITEBACK; + cf->metadata_version = 1; + cf->discard_passdown = true; +} + +static int parse_features(struct cache_args *ca, struct dm_arg_set *as, + char **error) +{ + static const struct dm_arg _args[] = { + {0, 3, "Invalid number of cache feature arguments"}, + }; + + int r, mode_ctr = 0; + unsigned int argc; + const char *arg; + struct cache_features *cf = &ca->features; + + init_features(cf); + + r = dm_read_arg_group(_args, as, &argc, error); + if (r) + return -EINVAL; + + while (argc--) { + arg = dm_shift_arg(as); + + if (!strcasecmp(arg, "writeback")) { + cf->io_mode = CM_IO_WRITEBACK; + mode_ctr++; + } + + else if (!strcasecmp(arg, "writethrough")) { + cf->io_mode = CM_IO_WRITETHROUGH; + mode_ctr++; + } + + else if (!strcasecmp(arg, "passthrough")) { + cf->io_mode = CM_IO_PASSTHROUGH; + mode_ctr++; + } + + else if (!strcasecmp(arg, "metadata2")) + cf->metadata_version = 2; + + else if (!strcasecmp(arg, "no_discard_passdown")) + cf->discard_passdown = false; + + else { + *error = "Unrecognised cache feature requested"; + return -EINVAL; + } + } + + if (mode_ctr > 1) { + *error = "Duplicate cache io_mode features requested"; + return -EINVAL; + } + + return 0; +} + +static int parse_policy(struct cache_args *ca, struct dm_arg_set *as, + char **error) +{ + static const struct dm_arg _args[] = { + {0, 1024, "Invalid number of policy arguments"}, + }; + + int r; + + if (!at_least_one_arg(as, error)) + return -EINVAL; + + ca->policy_name = dm_shift_arg(as); + + r = dm_read_arg_group(_args, as, &ca->policy_argc, error); + if (r) + return -EINVAL; + + ca->policy_argv = (const char **)as->argv; + dm_consume_args(as, ca->policy_argc); + + return 0; +} + +static int parse_cache_args(struct cache_args *ca, int argc, char **argv, + char **error) +{ + int r; + struct dm_arg_set as; + + as.argc = argc; + as.argv = argv; + + r = parse_metadata_dev(ca, &as, error); + if (r) + return r; + + r = parse_cache_dev(ca, &as, error); + if (r) + return r; + + r = parse_origin_dev(ca, &as, error); + if (r) + return r; + + r = parse_block_size(ca, &as, error); + if (r) + return r; + + r = parse_features(ca, &as, error); + if (r) + return r; + + r = parse_policy(ca, &as, error); + if (r) + return r; + + return 0; +} + +/*----------------------------------------------------------------*/ + +static struct kmem_cache *migration_cache; + +#define NOT_CORE_OPTION 1 + +static int process_config_option(struct cache *cache, const char *key, const char *value) +{ + unsigned long tmp; + + if (!strcasecmp(key, "migration_threshold")) { + if (kstrtoul(value, 10, &tmp)) + return -EINVAL; + + cache->migration_threshold = tmp; + return 0; + } + + return NOT_CORE_OPTION; +} + +static int set_config_value(struct cache *cache, const char *key, const char *value) +{ + int r = process_config_option(cache, key, value); + + if (r == NOT_CORE_OPTION) + r = policy_set_config_value(cache->policy, key, value); + + if (r) + DMWARN("bad config value for %s: %s", key, value); + + return r; +} + +static int set_config_values(struct cache *cache, int argc, const char **argv) +{ + int r = 0; + + if (argc & 1) { + DMWARN("Odd number of policy arguments given but they should be <key> <value> pairs."); + return -EINVAL; + } + + while (argc) { + r = set_config_value(cache, argv[0], argv[1]); + if (r) + break; + + argc -= 2; + argv += 2; + } + + return r; +} + +static int create_cache_policy(struct cache *cache, struct cache_args *ca, + char **error) +{ + struct dm_cache_policy *p = dm_cache_policy_create(ca->policy_name, + cache->cache_size, + cache->origin_sectors, + cache->sectors_per_block); + if (IS_ERR(p)) { + *error = "Error creating cache's policy"; + return PTR_ERR(p); + } + cache->policy = p; + BUG_ON(!cache->policy); + + return 0; +} + +/* + * We want the discard block size to be at least the size of the cache + * block size and have no more than 2^14 discard blocks across the origin. + */ +#define MAX_DISCARD_BLOCKS (1 << 14) + +static bool too_many_discard_blocks(sector_t discard_block_size, + sector_t origin_size) +{ + (void) sector_div(origin_size, discard_block_size); + + return origin_size > MAX_DISCARD_BLOCKS; +} + +static sector_t calculate_discard_block_size(sector_t cache_block_size, + sector_t origin_size) +{ + sector_t discard_block_size = cache_block_size; + + if (origin_size) + while (too_many_discard_blocks(discard_block_size, origin_size)) + discard_block_size *= 2; + + return discard_block_size; +} + +static void set_cache_size(struct cache *cache, dm_cblock_t size) +{ + dm_block_t nr_blocks = from_cblock(size); + + if (nr_blocks > (1 << 20) && cache->cache_size != size) + DMWARN_LIMIT("You have created a cache device with a lot of individual cache blocks (%llu)\n" + "All these mappings can consume a lot of kernel memory, and take some time to read/write.\n" + "Please consider increasing the cache block size to reduce the overall cache block count.", + (unsigned long long) nr_blocks); + + cache->cache_size = size; +} + +#define DEFAULT_MIGRATION_THRESHOLD 2048 + +static int cache_create(struct cache_args *ca, struct cache **result) +{ + int r = 0; + char **error = &ca->ti->error; + struct cache *cache; + struct dm_target *ti = ca->ti; + dm_block_t origin_blocks; + struct dm_cache_metadata *cmd; + bool may_format = ca->features.mode == CM_WRITE; + + cache = kzalloc(sizeof(*cache), GFP_KERNEL); + if (!cache) + return -ENOMEM; + + cache->ti = ca->ti; + ti->private = cache; + ti->accounts_remapped_io = true; + ti->num_flush_bios = 2; + ti->flush_supported = true; + + ti->num_discard_bios = 1; + ti->discards_supported = true; + + ti->per_io_data_size = sizeof(struct per_bio_data); + + cache->features = ca->features; + if (writethrough_mode(cache)) { + /* Create bioset for writethrough bios issued to origin */ + r = bioset_init(&cache->bs, BIO_POOL_SIZE, 0, 0); + if (r) + goto bad; + } + + cache->metadata_dev = ca->metadata_dev; + cache->origin_dev = ca->origin_dev; + cache->cache_dev = ca->cache_dev; + + ca->metadata_dev = ca->origin_dev = ca->cache_dev = NULL; + + origin_blocks = cache->origin_sectors = ca->origin_sectors; + origin_blocks = block_div(origin_blocks, ca->block_size); + cache->origin_blocks = to_oblock(origin_blocks); + + cache->sectors_per_block = ca->block_size; + if (dm_set_target_max_io_len(ti, cache->sectors_per_block)) { + r = -EINVAL; + goto bad; + } + + if (ca->block_size & (ca->block_size - 1)) { + dm_block_t cache_size = ca->cache_sectors; + + cache->sectors_per_block_shift = -1; + cache_size = block_div(cache_size, ca->block_size); + set_cache_size(cache, to_cblock(cache_size)); + } else { + cache->sectors_per_block_shift = __ffs(ca->block_size); + set_cache_size(cache, to_cblock(ca->cache_sectors >> cache->sectors_per_block_shift)); + } + + r = create_cache_policy(cache, ca, error); + if (r) + goto bad; + + cache->policy_nr_args = ca->policy_argc; + cache->migration_threshold = DEFAULT_MIGRATION_THRESHOLD; + + r = set_config_values(cache, ca->policy_argc, ca->policy_argv); + if (r) { + *error = "Error setting cache policy's config values"; + goto bad; + } + + cmd = dm_cache_metadata_open(cache->metadata_dev->bdev, + ca->block_size, may_format, + dm_cache_policy_get_hint_size(cache->policy), + ca->features.metadata_version); + if (IS_ERR(cmd)) { + *error = "Error creating metadata object"; + r = PTR_ERR(cmd); + goto bad; + } + cache->cmd = cmd; + set_cache_mode(cache, CM_WRITE); + if (get_cache_mode(cache) != CM_WRITE) { + *error = "Unable to get write access to metadata, please check/repair metadata."; + r = -EINVAL; + goto bad; + } + + if (passthrough_mode(cache)) { + bool all_clean; + + r = dm_cache_metadata_all_clean(cache->cmd, &all_clean); + if (r) { + *error = "dm_cache_metadata_all_clean() failed"; + goto bad; + } + + if (!all_clean) { + *error = "Cannot enter passthrough mode unless all blocks are clean"; + r = -EINVAL; + goto bad; + } + + policy_allow_migrations(cache->policy, false); + } + + spin_lock_init(&cache->lock); + bio_list_init(&cache->deferred_bios); + atomic_set(&cache->nr_allocated_migrations, 0); + atomic_set(&cache->nr_io_migrations, 0); + init_waitqueue_head(&cache->migration_wait); + + r = -ENOMEM; + atomic_set(&cache->nr_dirty, 0); + cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size)); + if (!cache->dirty_bitset) { + *error = "could not allocate dirty bitset"; + goto bad; + } + clear_bitset(cache->dirty_bitset, from_cblock(cache->cache_size)); + + cache->discard_block_size = + calculate_discard_block_size(cache->sectors_per_block, + cache->origin_sectors); + cache->discard_nr_blocks = to_dblock(dm_sector_div_up(cache->origin_sectors, + cache->discard_block_size)); + cache->discard_bitset = alloc_bitset(from_dblock(cache->discard_nr_blocks)); + if (!cache->discard_bitset) { + *error = "could not allocate discard bitset"; + goto bad; + } + clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks)); + + cache->copier = dm_kcopyd_client_create(&dm_kcopyd_throttle); + if (IS_ERR(cache->copier)) { + *error = "could not create kcopyd client"; + r = PTR_ERR(cache->copier); + goto bad; + } + + cache->wq = alloc_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM, 0); + if (!cache->wq) { + *error = "could not create workqueue for metadata object"; + goto bad; + } + INIT_WORK(&cache->deferred_bio_worker, process_deferred_bios); + INIT_WORK(&cache->migration_worker, check_migrations); + INIT_DELAYED_WORK(&cache->waker, do_waker); + + cache->prison = dm_bio_prison_create_v2(cache->wq); + if (!cache->prison) { + *error = "could not create bio prison"; + goto bad; + } + + r = mempool_init_slab_pool(&cache->migration_pool, MIGRATION_POOL_SIZE, + migration_cache); + if (r) { + *error = "Error creating cache's migration mempool"; + goto bad; + } + + cache->need_tick_bio = true; + cache->sized = false; + cache->invalidate = false; + cache->commit_requested = false; + cache->loaded_mappings = false; + cache->loaded_discards = false; + + load_stats(cache); + + atomic_set(&cache->stats.demotion, 0); + atomic_set(&cache->stats.promotion, 0); + atomic_set(&cache->stats.copies_avoided, 0); + atomic_set(&cache->stats.cache_cell_clash, 0); + atomic_set(&cache->stats.commit_count, 0); + atomic_set(&cache->stats.discard_count, 0); + + spin_lock_init(&cache->invalidation_lock); + INIT_LIST_HEAD(&cache->invalidation_requests); + + batcher_init(&cache->committer, commit_op, cache, + issue_op, cache, cache->wq); + dm_iot_init(&cache->tracker); + + init_rwsem(&cache->background_work_lock); + prevent_background_work(cache); + + *result = cache; + return 0; +bad: + destroy(cache); + return r; +} + +static int copy_ctr_args(struct cache *cache, int argc, const char **argv) +{ + unsigned int i; + const char **copy; + + copy = kcalloc(argc, sizeof(*copy), GFP_KERNEL); + if (!copy) + return -ENOMEM; + for (i = 0; i < argc; i++) { + copy[i] = kstrdup(argv[i], GFP_KERNEL); + if (!copy[i]) { + while (i--) + kfree(copy[i]); + kfree(copy); + return -ENOMEM; + } + } + + cache->nr_ctr_args = argc; + cache->ctr_args = copy; + + return 0; +} + +static int cache_ctr(struct dm_target *ti, unsigned int argc, char **argv) +{ + int r = -EINVAL; + struct cache_args *ca; + struct cache *cache = NULL; + + ca = kzalloc(sizeof(*ca), GFP_KERNEL); + if (!ca) { + ti->error = "Error allocating memory for cache"; + return -ENOMEM; + } + ca->ti = ti; + + r = parse_cache_args(ca, argc, argv, &ti->error); + if (r) + goto out; + + r = cache_create(ca, &cache); + if (r) + goto out; + + r = copy_ctr_args(cache, argc - 3, (const char **)argv + 3); + if (r) { + destroy(cache); + goto out; + } + + ti->private = cache; +out: + destroy_cache_args(ca); + return r; +} + +/*----------------------------------------------------------------*/ + +static int cache_map(struct dm_target *ti, struct bio *bio) +{ + struct cache *cache = ti->private; + + int r; + bool commit_needed; + dm_oblock_t block = get_bio_block(cache, bio); + + init_per_bio_data(bio); + if (unlikely(from_oblock(block) >= from_oblock(cache->origin_blocks))) { + /* + * This can only occur if the io goes to a partial block at + * the end of the origin device. We don't cache these. + * Just remap to the origin and carry on. + */ + remap_to_origin(cache, bio); + accounted_begin(cache, bio); + return DM_MAPIO_REMAPPED; + } + + if (discard_or_flush(bio)) { + defer_bio(cache, bio); + return DM_MAPIO_SUBMITTED; + } + + r = map_bio(cache, bio, block, &commit_needed); + if (commit_needed) + schedule_commit(&cache->committer); + + return r; +} + +static int cache_end_io(struct dm_target *ti, struct bio *bio, blk_status_t *error) +{ + struct cache *cache = ti->private; + unsigned long flags; + struct per_bio_data *pb = get_per_bio_data(bio); + + if (pb->tick) { + policy_tick(cache->policy, false); + + spin_lock_irqsave(&cache->lock, flags); + cache->need_tick_bio = true; + spin_unlock_irqrestore(&cache->lock, flags); + } + + bio_drop_shared_lock(cache, bio); + accounted_complete(cache, bio); + + return DM_ENDIO_DONE; +} + +static int write_dirty_bitset(struct cache *cache) +{ + int r; + + if (get_cache_mode(cache) >= CM_READ_ONLY) + return -EINVAL; + + r = dm_cache_set_dirty_bits(cache->cmd, from_cblock(cache->cache_size), cache->dirty_bitset); + if (r) + metadata_operation_failed(cache, "dm_cache_set_dirty_bits", r); + + return r; +} + +static int write_discard_bitset(struct cache *cache) +{ + unsigned int i, r; + + if (get_cache_mode(cache) >= CM_READ_ONLY) + return -EINVAL; + + r = dm_cache_discard_bitset_resize(cache->cmd, cache->discard_block_size, + cache->discard_nr_blocks); + if (r) { + DMERR("%s: could not resize on-disk discard bitset", cache_device_name(cache)); + metadata_operation_failed(cache, "dm_cache_discard_bitset_resize", r); + return r; + } + + for (i = 0; i < from_dblock(cache->discard_nr_blocks); i++) { + r = dm_cache_set_discard(cache->cmd, to_dblock(i), + is_discarded(cache, to_dblock(i))); + if (r) { + metadata_operation_failed(cache, "dm_cache_set_discard", r); + return r; + } + } + + return 0; +} + +static int write_hints(struct cache *cache) +{ + int r; + + if (get_cache_mode(cache) >= CM_READ_ONLY) + return -EINVAL; + + r = dm_cache_write_hints(cache->cmd, cache->policy); + if (r) { + metadata_operation_failed(cache, "dm_cache_write_hints", r); + return r; + } + + return 0; +} + +/* + * returns true on success + */ +static bool sync_metadata(struct cache *cache) +{ + int r1, r2, r3, r4; + + r1 = write_dirty_bitset(cache); + if (r1) + DMERR("%s: could not write dirty bitset", cache_device_name(cache)); + + r2 = write_discard_bitset(cache); + if (r2) + DMERR("%s: could not write discard bitset", cache_device_name(cache)); + + save_stats(cache); + + r3 = write_hints(cache); + if (r3) + DMERR("%s: could not write hints", cache_device_name(cache)); + + /* + * If writing the above metadata failed, we still commit, but don't + * set the clean shutdown flag. This will effectively force every + * dirty bit to be set on reload. + */ + r4 = commit(cache, !r1 && !r2 && !r3); + if (r4) + DMERR("%s: could not write cache metadata", cache_device_name(cache)); + + return !r1 && !r2 && !r3 && !r4; +} + +static void cache_postsuspend(struct dm_target *ti) +{ + struct cache *cache = ti->private; + + prevent_background_work(cache); + BUG_ON(atomic_read(&cache->nr_io_migrations)); + + cancel_delayed_work_sync(&cache->waker); + drain_workqueue(cache->wq); + WARN_ON(cache->tracker.in_flight); + + /* + * If it's a flush suspend there won't be any deferred bios, so this + * call is harmless. + */ + requeue_deferred_bios(cache); + + if (get_cache_mode(cache) == CM_WRITE) + (void) sync_metadata(cache); +} + +static int load_mapping(void *context, dm_oblock_t oblock, dm_cblock_t cblock, + bool dirty, uint32_t hint, bool hint_valid) +{ + struct cache *cache = context; + + if (dirty) { + set_bit(from_cblock(cblock), cache->dirty_bitset); + atomic_inc(&cache->nr_dirty); + } else + clear_bit(from_cblock(cblock), cache->dirty_bitset); + + return policy_load_mapping(cache->policy, oblock, cblock, dirty, hint, hint_valid); +} + +/* + * The discard block size in the on disk metadata is not + * necessarily the same as we're currently using. So we have to + * be careful to only set the discarded attribute if we know it + * covers a complete block of the new size. + */ +struct discard_load_info { + struct cache *cache; + + /* + * These blocks are sized using the on disk dblock size, rather + * than the current one. + */ + dm_block_t block_size; + dm_block_t discard_begin, discard_end; +}; + +static void discard_load_info_init(struct cache *cache, + struct discard_load_info *li) +{ + li->cache = cache; + li->discard_begin = li->discard_end = 0; +} + +static void set_discard_range(struct discard_load_info *li) +{ + sector_t b, e; + + if (li->discard_begin == li->discard_end) + return; + + /* + * Convert to sectors. + */ + b = li->discard_begin * li->block_size; + e = li->discard_end * li->block_size; + + /* + * Then convert back to the current dblock size. + */ + b = dm_sector_div_up(b, li->cache->discard_block_size); + sector_div(e, li->cache->discard_block_size); + + /* + * The origin may have shrunk, so we need to check we're still in + * bounds. + */ + if (e > from_dblock(li->cache->discard_nr_blocks)) + e = from_dblock(li->cache->discard_nr_blocks); + + for (; b < e; b++) + set_discard(li->cache, to_dblock(b)); +} + +static int load_discard(void *context, sector_t discard_block_size, + dm_dblock_t dblock, bool discard) +{ + struct discard_load_info *li = context; + + li->block_size = discard_block_size; + + if (discard) { + if (from_dblock(dblock) == li->discard_end) + /* + * We're already in a discard range, just extend it. + */ + li->discard_end = li->discard_end + 1ULL; + + else { + /* + * Emit the old range and start a new one. + */ + set_discard_range(li); + li->discard_begin = from_dblock(dblock); + li->discard_end = li->discard_begin + 1ULL; + } + } else { + set_discard_range(li); + li->discard_begin = li->discard_end = 0; + } + + return 0; +} + +static dm_cblock_t get_cache_dev_size(struct cache *cache) +{ + sector_t size = get_dev_size(cache->cache_dev); + (void) sector_div(size, cache->sectors_per_block); + return to_cblock(size); +} + +static bool can_resize(struct cache *cache, dm_cblock_t new_size) +{ + if (from_cblock(new_size) > from_cblock(cache->cache_size)) { + if (cache->sized) { + DMERR("%s: unable to extend cache due to missing cache table reload", + cache_device_name(cache)); + return false; + } + } + + /* + * We can't drop a dirty block when shrinking the cache. + */ + while (from_cblock(new_size) < from_cblock(cache->cache_size)) { + new_size = to_cblock(from_cblock(new_size) + 1); + if (is_dirty(cache, new_size)) { + DMERR("%s: unable to shrink cache; cache block %llu is dirty", + cache_device_name(cache), + (unsigned long long) from_cblock(new_size)); + return false; + } + } + + return true; +} + +static int resize_cache_dev(struct cache *cache, dm_cblock_t new_size) +{ + int r; + + r = dm_cache_resize(cache->cmd, new_size); + if (r) { + DMERR("%s: could not resize cache metadata", cache_device_name(cache)); + metadata_operation_failed(cache, "dm_cache_resize", r); + return r; + } + + set_cache_size(cache, new_size); + + return 0; +} + +static int cache_preresume(struct dm_target *ti) +{ + int r = 0; + struct cache *cache = ti->private; + dm_cblock_t csize = get_cache_dev_size(cache); + + /* + * Check to see if the cache has resized. + */ + if (!cache->sized) { + r = resize_cache_dev(cache, csize); + if (r) + return r; + + cache->sized = true; + + } else if (csize != cache->cache_size) { + if (!can_resize(cache, csize)) + return -EINVAL; + + r = resize_cache_dev(cache, csize); + if (r) + return r; + } + + if (!cache->loaded_mappings) { + r = dm_cache_load_mappings(cache->cmd, cache->policy, + load_mapping, cache); + if (r) { + DMERR("%s: could not load cache mappings", cache_device_name(cache)); + metadata_operation_failed(cache, "dm_cache_load_mappings", r); + return r; + } + + cache->loaded_mappings = true; + } + + if (!cache->loaded_discards) { + struct discard_load_info li; + + /* + * The discard bitset could have been resized, or the + * discard block size changed. To be safe we start by + * setting every dblock to not discarded. + */ + clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks)); + + discard_load_info_init(cache, &li); + r = dm_cache_load_discards(cache->cmd, load_discard, &li); + if (r) { + DMERR("%s: could not load origin discards", cache_device_name(cache)); + metadata_operation_failed(cache, "dm_cache_load_discards", r); + return r; + } + set_discard_range(&li); + + cache->loaded_discards = true; + } + + return r; +} + +static void cache_resume(struct dm_target *ti) +{ + struct cache *cache = ti->private; + + cache->need_tick_bio = true; + allow_background_work(cache); + do_waker(&cache->waker.work); +} + +static void emit_flags(struct cache *cache, char *result, + unsigned int maxlen, ssize_t *sz_ptr) +{ + ssize_t sz = *sz_ptr; + struct cache_features *cf = &cache->features; + unsigned int count = (cf->metadata_version == 2) + !cf->discard_passdown + 1; + + DMEMIT("%u ", count); + + if (cf->metadata_version == 2) + DMEMIT("metadata2 "); + + if (writethrough_mode(cache)) + DMEMIT("writethrough "); + + else if (passthrough_mode(cache)) + DMEMIT("passthrough "); + + else if (writeback_mode(cache)) + DMEMIT("writeback "); + + else { + DMEMIT("unknown "); + DMERR("%s: internal error: unknown io mode: %d", + cache_device_name(cache), (int) cf->io_mode); + } + + if (!cf->discard_passdown) + DMEMIT("no_discard_passdown "); + + *sz_ptr = sz; +} + +/* + * Status format: + * + * <metadata block size> <#used metadata blocks>/<#total metadata blocks> + * <cache block size> <#used cache blocks>/<#total cache blocks> + * <#read hits> <#read misses> <#write hits> <#write misses> + * <#demotions> <#promotions> <#dirty> + * <#features> <features>* + * <#core args> <core args> + * <policy name> <#policy args> <policy args>* <cache metadata mode> <needs_check> + */ +static void cache_status(struct dm_target *ti, status_type_t type, + unsigned int status_flags, char *result, unsigned int maxlen) +{ + int r = 0; + unsigned int i; + ssize_t sz = 0; + dm_block_t nr_free_blocks_metadata = 0; + dm_block_t nr_blocks_metadata = 0; + char buf[BDEVNAME_SIZE]; + struct cache *cache = ti->private; + dm_cblock_t residency; + bool needs_check; + + switch (type) { + case STATUSTYPE_INFO: + if (get_cache_mode(cache) == CM_FAIL) { + DMEMIT("Fail"); + break; + } + + /* Commit to ensure statistics aren't out-of-date */ + if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti)) + (void) commit(cache, false); + + r = dm_cache_get_free_metadata_block_count(cache->cmd, &nr_free_blocks_metadata); + if (r) { + DMERR("%s: dm_cache_get_free_metadata_block_count returned %d", + cache_device_name(cache), r); + goto err; + } + + r = dm_cache_get_metadata_dev_size(cache->cmd, &nr_blocks_metadata); + if (r) { + DMERR("%s: dm_cache_get_metadata_dev_size returned %d", + cache_device_name(cache), r); + goto err; + } + + residency = policy_residency(cache->policy); + + DMEMIT("%u %llu/%llu %llu %llu/%llu %u %u %u %u %u %u %lu ", + (unsigned int)DM_CACHE_METADATA_BLOCK_SIZE, + (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata), + (unsigned long long)nr_blocks_metadata, + (unsigned long long)cache->sectors_per_block, + (unsigned long long) from_cblock(residency), + (unsigned long long) from_cblock(cache->cache_size), + (unsigned int) atomic_read(&cache->stats.read_hit), + (unsigned int) atomic_read(&cache->stats.read_miss), + (unsigned int) atomic_read(&cache->stats.write_hit), + (unsigned int) atomic_read(&cache->stats.write_miss), + (unsigned int) atomic_read(&cache->stats.demotion), + (unsigned int) atomic_read(&cache->stats.promotion), + (unsigned long) atomic_read(&cache->nr_dirty)); + + emit_flags(cache, result, maxlen, &sz); + + DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold); + + DMEMIT("%s ", dm_cache_policy_get_name(cache->policy)); + if (sz < maxlen) { + r = policy_emit_config_values(cache->policy, result, maxlen, &sz); + if (r) + DMERR("%s: policy_emit_config_values returned %d", + cache_device_name(cache), r); + } + + if (get_cache_mode(cache) == CM_READ_ONLY) + DMEMIT("ro "); + else + DMEMIT("rw "); + + r = dm_cache_metadata_needs_check(cache->cmd, &needs_check); + + if (r || needs_check) + DMEMIT("needs_check "); + else + DMEMIT("- "); + + break; + + case STATUSTYPE_TABLE: + format_dev_t(buf, cache->metadata_dev->bdev->bd_dev); + DMEMIT("%s ", buf); + format_dev_t(buf, cache->cache_dev->bdev->bd_dev); + DMEMIT("%s ", buf); + format_dev_t(buf, cache->origin_dev->bdev->bd_dev); + DMEMIT("%s", buf); + + for (i = 0; i < cache->nr_ctr_args - 1; i++) + DMEMIT(" %s", cache->ctr_args[i]); + if (cache->nr_ctr_args) + DMEMIT(" %s", cache->ctr_args[cache->nr_ctr_args - 1]); + break; + + case STATUSTYPE_IMA: + DMEMIT_TARGET_NAME_VERSION(ti->type); + if (get_cache_mode(cache) == CM_FAIL) + DMEMIT(",metadata_mode=fail"); + else if (get_cache_mode(cache) == CM_READ_ONLY) + DMEMIT(",metadata_mode=ro"); + else + DMEMIT(",metadata_mode=rw"); + + format_dev_t(buf, cache->metadata_dev->bdev->bd_dev); + DMEMIT(",cache_metadata_device=%s", buf); + format_dev_t(buf, cache->cache_dev->bdev->bd_dev); + DMEMIT(",cache_device=%s", buf); + format_dev_t(buf, cache->origin_dev->bdev->bd_dev); + DMEMIT(",cache_origin_device=%s", buf); + DMEMIT(",writethrough=%c", writethrough_mode(cache) ? 'y' : 'n'); + DMEMIT(",writeback=%c", writeback_mode(cache) ? 'y' : 'n'); + DMEMIT(",passthrough=%c", passthrough_mode(cache) ? 'y' : 'n'); + DMEMIT(",metadata2=%c", cache->features.metadata_version == 2 ? 'y' : 'n'); + DMEMIT(",no_discard_passdown=%c", cache->features.discard_passdown ? 'n' : 'y'); + DMEMIT(";"); + break; + } + + return; + +err: + DMEMIT("Error"); +} + +/* + * Defines a range of cblocks, begin to (end - 1) are in the range. end is + * the one-past-the-end value. + */ +struct cblock_range { + dm_cblock_t begin; + dm_cblock_t end; +}; + +/* + * A cache block range can take two forms: + * + * i) A single cblock, eg. '3456' + * ii) A begin and end cblock with a dash between, eg. 123-234 + */ +static int parse_cblock_range(struct cache *cache, const char *str, + struct cblock_range *result) +{ + char dummy; + uint64_t b, e; + int r; + + /* + * Try and parse form (ii) first. + */ + r = sscanf(str, "%llu-%llu%c", &b, &e, &dummy); + if (r < 0) + return r; + + if (r == 2) { + result->begin = to_cblock(b); + result->end = to_cblock(e); + return 0; + } + + /* + * That didn't work, try form (i). + */ + r = sscanf(str, "%llu%c", &b, &dummy); + if (r < 0) + return r; + + if (r == 1) { + result->begin = to_cblock(b); + result->end = to_cblock(from_cblock(result->begin) + 1u); + return 0; + } + + DMERR("%s: invalid cblock range '%s'", cache_device_name(cache), str); + return -EINVAL; +} + +static int validate_cblock_range(struct cache *cache, struct cblock_range *range) +{ + uint64_t b = from_cblock(range->begin); + uint64_t e = from_cblock(range->end); + uint64_t n = from_cblock(cache->cache_size); + + if (b >= n) { + DMERR("%s: begin cblock out of range: %llu >= %llu", + cache_device_name(cache), b, n); + return -EINVAL; + } + + if (e > n) { + DMERR("%s: end cblock out of range: %llu > %llu", + cache_device_name(cache), e, n); + return -EINVAL; + } + + if (b >= e) { + DMERR("%s: invalid cblock range: %llu >= %llu", + cache_device_name(cache), b, e); + return -EINVAL; + } + + return 0; +} + +static inline dm_cblock_t cblock_succ(dm_cblock_t b) +{ + return to_cblock(from_cblock(b) + 1); +} + +static int request_invalidation(struct cache *cache, struct cblock_range *range) +{ + int r = 0; + + /* + * We don't need to do any locking here because we know we're in + * passthrough mode. There's is potential for a race between an + * invalidation triggered by an io and an invalidation message. This + * is harmless, we must not worry if the policy call fails. + */ + while (range->begin != range->end) { + r = invalidate_cblock(cache, range->begin); + if (r) + return r; + + range->begin = cblock_succ(range->begin); + } + + cache->commit_requested = true; + return r; +} + +static int process_invalidate_cblocks_message(struct cache *cache, unsigned int count, + const char **cblock_ranges) +{ + int r = 0; + unsigned int i; + struct cblock_range range; + + if (!passthrough_mode(cache)) { + DMERR("%s: cache has to be in passthrough mode for invalidation", + cache_device_name(cache)); + return -EPERM; + } + + for (i = 0; i < count; i++) { + r = parse_cblock_range(cache, cblock_ranges[i], &range); + if (r) + break; + + r = validate_cblock_range(cache, &range); + if (r) + break; + + /* + * Pass begin and end origin blocks to the worker and wake it. + */ + r = request_invalidation(cache, &range); + if (r) + break; + } + + return r; +} + +/* + * Supports + * "<key> <value>" + * and + * "invalidate_cblocks [(<begin>)|(<begin>-<end>)]* + * + * The key migration_threshold is supported by the cache target core. + */ +static int cache_message(struct dm_target *ti, unsigned int argc, char **argv, + char *result, unsigned int maxlen) +{ + struct cache *cache = ti->private; + + if (!argc) + return -EINVAL; + + if (get_cache_mode(cache) >= CM_READ_ONLY) { + DMERR("%s: unable to service cache target messages in READ_ONLY or FAIL mode", + cache_device_name(cache)); + return -EOPNOTSUPP; + } + + if (!strcasecmp(argv[0], "invalidate_cblocks")) + return process_invalidate_cblocks_message(cache, argc - 1, (const char **) argv + 1); + + if (argc != 2) + return -EINVAL; + + return set_config_value(cache, argv[0], argv[1]); +} + +static int cache_iterate_devices(struct dm_target *ti, + iterate_devices_callout_fn fn, void *data) +{ + int r = 0; + struct cache *cache = ti->private; + + r = fn(ti, cache->cache_dev, 0, get_dev_size(cache->cache_dev), data); + if (!r) + r = fn(ti, cache->origin_dev, 0, ti->len, data); + + return r; +} + +/* + * If discard_passdown was enabled verify that the origin device + * supports discards. Disable discard_passdown if not. + */ +static void disable_passdown_if_not_supported(struct cache *cache) +{ + struct block_device *origin_bdev = cache->origin_dev->bdev; + struct queue_limits *origin_limits = &bdev_get_queue(origin_bdev)->limits; + const char *reason = NULL; + + if (!cache->features.discard_passdown) + return; + + if (!bdev_max_discard_sectors(origin_bdev)) + reason = "discard unsupported"; + + else if (origin_limits->max_discard_sectors < cache->sectors_per_block) + reason = "max discard sectors smaller than a block"; + + if (reason) { + DMWARN("Origin device (%pg) %s: Disabling discard passdown.", + origin_bdev, reason); + cache->features.discard_passdown = false; + } +} + +static void set_discard_limits(struct cache *cache, struct queue_limits *limits) +{ + struct block_device *origin_bdev = cache->origin_dev->bdev; + struct queue_limits *origin_limits = &bdev_get_queue(origin_bdev)->limits; + + if (!cache->features.discard_passdown) { + /* No passdown is done so setting own virtual limits */ + limits->max_discard_sectors = min_t(sector_t, cache->discard_block_size * 1024, + cache->origin_sectors); + limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT; + return; + } + + /* + * cache_iterate_devices() is stacking both origin and fast device limits + * but discards aren't passed to fast device, so inherit origin's limits. + */ + limits->max_discard_sectors = origin_limits->max_discard_sectors; + limits->max_hw_discard_sectors = origin_limits->max_hw_discard_sectors; + limits->discard_granularity = origin_limits->discard_granularity; + limits->discard_alignment = origin_limits->discard_alignment; + limits->discard_misaligned = origin_limits->discard_misaligned; +} + +static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits) +{ + struct cache *cache = ti->private; + uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT; + + /* + * If the system-determined stacked limits are compatible with the + * cache's blocksize (io_opt is a factor) do not override them. + */ + if (io_opt_sectors < cache->sectors_per_block || + do_div(io_opt_sectors, cache->sectors_per_block)) { + blk_limits_io_min(limits, cache->sectors_per_block << SECTOR_SHIFT); + blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT); + } + + disable_passdown_if_not_supported(cache); + set_discard_limits(cache, limits); +} + +/*----------------------------------------------------------------*/ + +static struct target_type cache_target = { + .name = "cache", + .version = {2, 2, 0}, + .module = THIS_MODULE, + .ctr = cache_ctr, + .dtr = cache_dtr, + .map = cache_map, + .end_io = cache_end_io, + .postsuspend = cache_postsuspend, + .preresume = cache_preresume, + .resume = cache_resume, + .status = cache_status, + .message = cache_message, + .iterate_devices = cache_iterate_devices, + .io_hints = cache_io_hints, +}; + +static int __init dm_cache_init(void) +{ + int r; + + migration_cache = KMEM_CACHE(dm_cache_migration, 0); + if (!migration_cache) + return -ENOMEM; + + r = dm_register_target(&cache_target); + if (r) { + kmem_cache_destroy(migration_cache); + return r; + } + + return 0; +} + +static void __exit dm_cache_exit(void) +{ + dm_unregister_target(&cache_target); + kmem_cache_destroy(migration_cache); +} + +module_init(dm_cache_init); +module_exit(dm_cache_exit); + +MODULE_DESCRIPTION(DM_NAME " cache target"); +MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>"); +MODULE_LICENSE("GPL"); |